How Spectacles Have Been Used To Correct Visual Errors

The strength of reading glasses was originally based on the patient's age. For a man of 30"40 years lenses of 2 degrees were used, for 70"80 years, lenses of 4 degrees. It wasn't until the middle of the 19th century that glasses started to be issued by people who knew some basics about optics.

It is remarkable that in our present scientific age, when the appropriate corrective lenses can be prescribed on the basis of precise measurement of refractive errors, some people still choose their own reading eyeglasses at the chemist's shop.

Astigmatic correction was not generally available until late in the nineteenth century, despite Airy's cylindrical correcting lens (1827) and Donders' comprehensive book on refraction (1864). Many inventive solutions come out of necessity and it was the same for bifocal lenses. Benjamin Franklin - yes THE Benjamin Franklin, needed to devise bifocal lenses for himself and so he split apart the lenses in his reading and distance glasses and just stuck them together - Hey Presto: Bifocals were invented.

In 1826, Hawkins brought out a range of trifocal lenses. Smoothly increasing multifocal lenses, were then brought in about 100 years later. Although, these did sound like a good idea in theory, it turned out that they were effectively useless as they didn't allow enough clear vision in the in between sections.

It may be that multifocal lenses do have a role in patients with emerging multifocal lenses, as they may be better positions to tolerate the increasing strengths.